This invention relates to the construction and method for making musical instrument strings. More particularly, it relates to strings having superior corrosion resistance and longevity, low stiffness for improved playability and tonal quality, and low tension at pitch for reduced stress on musical instruments. The present invention is particularly adapted for use with bridged stringed instruments including classical guitar, steel string guitar, violin, cello, dulcimer, banjo, mandolin, bass, etc.
It is well known that strings under tension will vibrate when plucked, struck, or bowed at a characteristic fundamental frequency f1, accompanied by a spectrum of n harmonic frequencies, all proportional to the tension and inversely proportional to the mass per unit length of the string (Jeans, Sir James, Science And Music, Dover Publications, Inc., New York, 1937, reprinted 1968). This relationship can be expressed for an ideal string of zero stiffness by equation 1:
fn=(n/2L)(T/m)xc2xdxe2x80x83xe2x80x83[1]
where fn is the frequency of the nth harmonic, L is the speaking length of the string, T is the tension, and m is the mass per unit length.
In many cases, this ideal relationship can be used to adequately approximate the fundamental frequency as well as the first few harmonics for real strings under tension. However, since real materials have finite stiff-ness values, they do not completely obey the ideal relationship depicted above (Elmore, W. C. and Heald, M. A., Physics of Waves, Dover Publications, Inc., 1969). Instead, the stiffness of a real string will contribute to the elastic restoring force during string vibration, leading to inharmonicity, particularly with respect to the higher harmonics. Thus, when designing strings for musical instruments, these factors must be considered together with several other limiting factors of practical concern, including the xe2x80x9cwindow of tensionxe2x80x9d for a particular instrument, the physical properties of both core and winding materials, and the suitability of materials for string fabrication.
For example, lower frequency musical instrument strings are often helically wound with mass loading materials such as alloys of copper, steel and nickel so that the unit mass can be controlled within some xe2x80x9cwindow of tensionxe2x80x9d without having to increase the speaking length or the mass of the core string. Otherwise, the speaking lengths for bass strings would be unrealistically long, and/or the diameter and mass would be too high, leading to high stiff-ness, reduced tonal quality, and difficulty with fingering during instrument play.
The xe2x80x9cwindow of tensionxe2x80x9d is determined in part by the construction and design of the instrument, and specifically by the cumulative tension that can be sustained when a plural set of strings is tuned to pitch. Thus, if the tension is maintained at too high of a value, the instrument can be permanently damaged. If the tension is too low, then unwanted resonances and buzzing noises may occur. For example, the cumulative tension for strings on a xe2x80x9cclassical guitarxe2x80x9d is typically between 75 and 100 pounds, whereas the cumulative tension on a steel-stringed acoustic guitar can be as high as 190 pounds.
Like string stiffness, tension can also affect xe2x80x9cplaying actionxe2x80x9d, or the pressure required for fretting during play. There is some latitude for tension adjustment with conventional string materials, as long as the cumulative tension falls within the xe2x80x9cwindow of tensionxe2x80x9d that provides the best overall response from the instrument. For example, it is possible to reduce the diameter and hence stiffness and tension of steel core strings, but only to the point where the strength, loudness, and sound quality are not seriously compromised.
In addition to the xe2x80x9cwindow of tensionxe2x80x9d, musical instrument string designers are constrained by the physical properties of conventional materials. Although some material improvements have been made, the most commonly used materials for the cores of wound musical instrument strings still include polymers such as synthetic nylon or natural xe2x80x9cgutxe2x80x9d, and steel (for example, music spring wire that is currently manufactured according to ASTM A228 specifications).
A core material must have the ability to maintain dimensional stability without breaking under tension. Hence it must possess the combined characteristics of high tensile strength, low creep, high yield strength, and low ductility. On the other hand, windings, such as those used with conventionally wound steel core strings, are typically made of softer, more ductile metals such as alloys of copper, steel, or nickel. These alloys can possess various degrees of hardness or temper, and are typically chosen for their ability to control the mass per unit length, and for their ductility or yield characteristics for ease of manufacturing.
Although the use of metal windings has historically enabled designers to control mass per unit length and hence pitch, one inherent problem with wound strings is that the windings tend to move, slip, and re-position themselves with respect to the core during end use. This leads to increasingly higher frictional losses and vibrational damping, with the upper harmonic frequencies being particularly affected. Gradually, the tonal quality deteriorates and the string loses its xe2x80x9clivelinessxe2x80x9d and xe2x80x9cbrilliancexe2x80x9d. The problem may be partly related to stress relaxation from winding recoil, but it is also compounded by interfacial deterioration from corrosion at the core/winding interfaces, and from yielding of ductile interfacial materials such as tin or tin alloys. Steel core corrosion byproducts such as Fe2O3 are also weak oxides, and can easily spall, leading to mechanical losses and oxide particle contamination which can further dampen vibrations and negatively impact tonal quality. Together, these problems ultimately lead to what many musicians recognize as a xe2x80x9cdeadxe2x80x9d string.
Furthermore, conventional strings have a limited shelf-life, and often require special packaging considerations and/or storage conditions to prevent corrosion, and to preserve their tonal characteristics prior to use. In some cases, strings which have been stored for long periods can become weakened from corrosion, and can break when attempts are made to tune the strings to pitch. In other cases, the otherwise xe2x80x9cnewxe2x80x9d strings can exhibit the tonal characteristics of xe2x80x9cdeadxe2x80x9d strings simply because they were stored too long before use.
Several prior art examples have addressed one or more of these issues through methods and constructions aimed at improving the longevity of wound strings. U.S. Pat. No. 210,172 to Watson and Bauer (1878) disclosed the first use of polygonal shaped core wires that unlike round cores, help to prevent winding recoil both during manufacture and in end use. This technology is still commonly used today for steel core wires of wound guitar strings such as the hexagonal steel cores used by J. D""Addario and Company, Inc. in their Phosphor Bronze wound acoustic guitar strings.
U.S. Pat. No. 2,746,335 to Johnson (1956) discloses a concentrically wound core wire where the inner wire is terminated in a tapered gripping fashion over a flattened section near the core end. The purpose is to maintain winding tightness and to prevent buzzing. U.S. Pat. No. 5,535,658 to Kalosdian (1996) discloses a plurality of metallic inner wrap wires wound about a central metallic core, and concentrically wound with an outer wrap of metallic wire over the speaking length of the string to maintain tightness of the inner windings over time. The outer wrap traverses the speaking length of the string and thus it contributes to the mass per unit length, the tonal quality, the diameter, and the string stiffness accordingly. U.S. Pat. No. 3,605,544 to Kondo (1971) discloses a musical instrument string with a core wire and a helically wound covering wire where the winding pitch is greater than the diameter of the covering wire. The purpose is to eliminate contact between adjacent turns so that frictional losses at winding interfaces can be eliminated.
Several other prior art examples teach of constructions and methods aimed at improving the properties of musical instrument strings. U.S. Pat. No. 4,539,228 to Lazarus (1985) discloses a method for treating wound musical instrument strings to reduce the xe2x80x9cbreak-in periodxe2x80x9d and to extend useful life by filling microscopic pores, cavities, and interstitial spaces of wound strings with dry lubricant particles, moisture displacement agents, and corrosion inhibitor.
U.S. Pat. Nos. 5,883,319 and 5,907,113 to Hebestreit, et al. (1999) disclose wound and non-wound musical instrument strings that are covered with a porous polytetrafluoroethylene polymer over a portion of the speaking length, or over the entire speaking length of the string for the purpose of providing corrosion resistance, comfortable play, less finger noise, and longer life (these strings are commercially available from W. L. Gore and Associates, Inc.). The coating traverses the speaking length of the string and therefore modulates the tonal and dampening characteristics accordingly.
U.S. Pat. No. 2,892,374 to Ralls (1959) discloses a conditioning process where a musical instrument string with a metallic winding wrapped about a gut core is treated by soaking the strings in a polymer lacquer solution to coat the core and to fill the interstitial spaces between core and windings along the entire speaking length of the string. The purpose is to prevent shrinkage of the gut core and to prevent loosening of windings during end use, both of which lengthen string life. Similarly, since the polymer traverses the entire speaking length, tonal quality, stiffness, and playability are affected accordingly.
U.S. Pat. No. 2,049,769 to Gray (1936) discloses a string constructed with a varnish reinforced fabric that encircles a straight or kinked metal core along its entire length to form a unitary string body. Metal windings can be incorporated either between the fabric and core, or they can be wrapped around the unitary composite core. This string owes its properties to its composite nature, where the fabric is incorporated to carry a portion of the tensile load in concert with a steel core wire. The polymer and fabric traverse the entire speaking length, so tonal qualities, dampening, stiffness, and playability are all affected.
U.S. Pat. No. 5,578,775 to Ito (1996) discloses an instrument string made with a composite core of fibrous materials such as carbon, ceramic, or metal; and sheathed with ductile precious metals such as gold, platinum or silver for modulation of mass per unit length, and for aesthetic value. The fibers provide the reinforcement required for a high strength core, and the metal sheathing provides the ability to modulate mass per unit length as well as to provide a surface with high ductility. This highly ductile surface also becomes the area of contact between the winding and the core. The same precious metal composite is disclosed for use as a winding either on a steel core, on an organic core, or on a similar composite core.
U.S. Pat. No. 5,817,960 to Sanderson (1998) discloses concentrically wrapped wires about a central core, where the first is wrapped along the entire core length, and the second is wrapped over or under the first near the core end. The second wrap wire only serves to compensate for inharmonicity introduced by a bare end wire.
U.S. Pat. No. 2,710,557 to Sundt (1955) discloses a set of musical instrument strings where the wound strings are composed of a plurality of small diameter wires bound in composite form by an elastomeric polymer over the entire speaking length of the string. The elastomer provides a base over which windings can be tightly wound. The elastomer also contributes to the tonal and damping characteristics of the string since it traverses the entire speaking length.
U.S. Pat. No. 5,704,473 to Oster (1998) discloses musical instrument strings and controlled atmosphere packaging with a flexible polymer material covering the end opposite the ball end of the string for the purpose of color identifying strings that are packaged together in a single pouch, where the pouch is designed to hold a non corrosive gas to reduce string corrosion. The coating is formed through a liquid dip/cure process and is also designed to be either permanent or removable after the string end is inserted through the tuning post of the musical instrument. The coating reduces the hazard of injury when uncoiling the string.
Although several of these references disclose string constructions and methods for enhancing string life by some combination of either slowing corrosion, or by adhesively/mechanically maintaining tight windings over time, none of these teachings address the fundamental problem of preventing corrosion. Many traditional metal wound steel core strings are inherently flawed from the standpoint that the junction points between windings and the steel core provide the potential for galvanic coupling and corrosion. The corrosion process can be readily accelerated by moisture and ions from dissociated salts, organic acids, or other contaminates that originate from human hands during instrument use. These conventional constructions are also known to oxidize and corrode from simple atmospheric exposure, which greatly limits shelf life, and causes string deterioration even before end-use.
It is generally known that corrosion of the anodic component in a galvanic couple is accelerated as the ratio of the surface area of the cathodic metal to the anodic metal increases (Metals Handbook Desk Edition, second edition, J. R. Davis-Editor, ASM International, Materials Park, Ohio, 1998). In the case of conventionally wound steel core strings, the steel core is typically the more anodic of the coupled pair, and it also has the least amount of exposed surface area. Even worse, the iron oxides that form at the anode are mechanically weak oxides, which easily spall, leading ultimately to shearing motions and contamination at multiple interfaces, and vibrational dampening in the form of frictional heat dissipation. In order to minimize corrosion, it would be desirable to either construct the string with electrochemically equivalent materials, or if some degree of galvanic coupling is inevitable, to design by minimizing the surface area of the cathodic member. However, no such design has been implemented to date with steel core musical instrument strings.
Instead, many steel cores for wound guitar strings are typically surface treated with malleable metals such as tin, tin alloys, gold, or silver for the purpose of decreasing the rate of corrosion, and for helping to maintain initial winding tightness. U.S. Pat. No. 4,063,674 to Stone and Falcone (1977) discloses a method of manufacture whereby a wound string assembly is heated at an elevated temperature for various amounts of time to produce a string where windings are more evenly spaced. The coefficient of thermal expansion of the core is less than that of the winding, and the core is coated with a material having a melting point lower than the heat treatment temperature. The invention discloses a tin coating that upon heating, can be used to form a metallurgical bond between winding and core.
It is generally known that surface coatings such as tin can reduce the galvanic couple between steel and other metallic materials, but corrosion is not entirely prevented (see for example McKay, R. J. and Worthington, R., Corrosion Resistance of Metals and Alloys, American Chemical Society Monograph Series, Reinhold Publishing Corporation, New York, 1936). The malleability of Sn can enable it to yield and partially encase the winding during processing to help maintain initial tightness. However, this same attribute can also be a long term detriment since the ductility of tin renders it susceptible to yielding under the recoil stress of the windings, a problem which is further aggravated by corrosion since bi-products may further weaken the material near the chemically dissimilar interfaces. Thus, short term durability and ultimate interfacial failure are simultaneously and paradoxically inherent to the structural design of many conventional metal wound steel core strings.
In cases where polymers or lacquers have been used to either slow corrosion or to maintain winding tightness, they traverse either a portion of, or the entire speaking length of the string, and thus they influence the tonal and dampening characteristics of the string.
Alternatively, lower density polymeric strings such as gut and nylon are not susceptible to corrosion, and are used either alone or as the cores for metallic or polymeric wound strings. However, due to their organic nature, these types of strings are characterized by different dampening and tonal characteristics, and are used in cases where either different tonal characteristics are desired, or where lower tensions are mandated by virtue of instrument design.
When metal strings are desired for their tonal qualities, or for their magnetic properties as in the case of electric guitars with magnetic pickups, it becomes necessary to reinforce the construction of the musical instrument so that it can support and sustain the higher stress loadings. In the case of acoustic guitar bodies, this is accomplished through the incorporation of metal neck reinforcement bars, bridgeplate reinforcements, and other sound board reinforcements that help to prevent warpage and failure of instrument body components. Consequently, the need for a higher strength instrument body for use with steel core strings has necessarily limited the design and material possibilities for the construction of such instruments.
For example, when compared to a steel string guitar, a classical guitar is designed with less reinforcement under the sound board and near the bridgeplate. Thus, the resonating members of a classical guitar are lower in stiffness, which reduces the dampening contribution that is otherwise present with additional reinforcement materials. The tonal qualities of metallic core strings on such an instrument might in theory be aesthetically pleasing, but the possibility cannot be tested with current metal wound acoustic strings at conventional diameters, since their high cumulative tensions would damage or even destroy the instrument. Thus, there exists a need for low tension metallic strings that could be used on existing classical instruments. Such strings would also expand the material and design possibilities for instrument designers and manufacturers.
Another shortcoming of conventional wound strings results from the use of ball ends, which serve to fasten the string to the bridge of a stringed instrument. For example, the core of a guitar string is typically looped around an annular, spool shaped xe2x80x9cball endxe2x80x9d, and is then wound around itself to hold the end in place. This results in a transition step where subsequent slippage of windings can occur when the wound string is placed under tension. Winding slippage can often be heard as audible xe2x80x9cbridge noisesxe2x80x9d during the first tuning of a new string, and can also continue during end use. As with any process which leads to winding slippage, this phenomenon can lead to changes in tuning, changes in intonation, or string deadening if the effect is longitudinally propagated over the speaking length of the string. This area of the string is also stiffer and higher in diameter than the remainder of the string. Thus, when the string is placed under tension, it can place additional stress on the instrument bridge, which is typically made of softer wood on acoustic instruments. This bridge stress is compounded by the use of conventional steel core wound strings, since high tensions are required to tune these strings to pitch on stringed instruments. Over time, this localized bridge stress results in xe2x80x9cgroovingxe2x80x9d and deterioration of the softer wood. Hence, a need exists for a string with a modified end which reduces the stress on the bridge, and which also prevents windings from slipping during use.
Accordingly, it would be desirable and advantageous to develop a string construction where the galvanic couple between the contact metal surfaces is either eliminated, or where the lowest surface area member is the more cathodic member of the galvanic couple. It would also be desirable and advantageous to eliminate the use of malleable and ductile materials at the interface between the windings and core over the speaking length of the string so that the potential for long term yielding can be minimized during end-use. It would also be desirable to minimize or eliminate the use of any material within the speaking length of the string (other than core and winding) that can adversely influence the damping characteristics and hence affect tonal quality. It would also be advantageous to develop a metallic core string with the aforementioned characteristics that can be tuned to pitch at reduced tension so that when used in plurality on a stringed instrument, reduced cumulative tension is delivered to the instrument bridge, hence reducing instrument wear and prolonging instrument life. Still further, it would be advantageous to have a metallic instrument string that can be tuned to pitch at a sufficiently reduced tension so that when used in plurality as a set, the cumulative tension is low enough to render it useful for classical body constructions that are characterized by less structural reinforcement than their steel-stringed guitar counterparts. Finally, it would be advantageous for the instrument string to have reduced stiffness for better tonal characteristics (less inharmonicity), and for easier playability.
Accordingly, it is a primary object of the present invention is to provide a wound metallic musical instrument string with combined attributes of high corrosion resistance, low tension at pitch, and low stiffness.
Another object is to provide a musical instrument string with the benefits of lower stiffness including ease of play, and better tonal qualities.
Another object is to provide a musical instrument string with the benefits of improved corrosion resistance including longer shelf life before use, and longer life during end use.
Still another object of the present invention is to provide a plurality of metallic musical instrument strings that can be tuned to pitch at a sufficiently reduced tension, so that the cumulative tension is low enough to render the set useful for instrument body constructions that are characterized by less structural reinforcement than their steel string counterparts.
Yet another object of the present invention is to provide a method for manufacturing the strings of this invention whereby the tightness of windings is maintained both during manufacture and in end use.
Still another object is to provide a method for maintaining tight windings without ductile metals between the winding and core interfaces over the speaking length of the string.
Still another object is to provide a method for maintaining tight windings without the use of dampening polymeric materials within the speaking length of the string.
Another object of this invention is to provide a musical instrument string that protects the wood on the bridge of a musical instrument from wear which otherwise occurs from the continued use of unprotected metal strings.
These and other objects and advantages of the present invention will be more fully understood and appreciated with reference to the following description.
The present invention relates to an improved musical instrument string for use on instruments including but not limited to guitars, violins, mandolins, cellos, pianos, basses, etc. This invention is particularly suitable for use on instruments where the strings are handled during play such as guitars, basses and other hand held stringed instruments.
The string of the present invention employs a metallic core which can be spirally wound to produce lower pitched notes, where the core is either electrochemically equivalent to the winding, or is the more cathodic member of the coupled pair. The preferred string comprises a metal core of a titanium alloy wire, and a winding of either titanium, or a galvanically similar material such as nickel, a nickel alloy, or bronze. The string of the present invention is unique over all previous attempts to construct metallic strings in that the titanium alloy core is more cathodic, less dense, lower in modulus, and sufficiently strengthened so as to achieve the necessary tensile and yield characteristics to maintain pitch under tension without breaking. Unlike steel core strings, this string will resist corrosion for much longer durations of time. Also, the lower density translates to reduced tension at pitch, and hence longer instrument life, and easier playability. The lower modulus also equates to lower stiffness at an equivalent diameter core, which translates to improved tonal quality, and easier fretting during instrument use.
It has been determined that as the winding wire in the present invention becomes more anodic, corrosion of the winding can occur, but not corrosion of the core. Thus, the most preferred winding wire is one that is electrochemically matched to titanium. Nickel and titanium have been found to be exceptionally good materials for this purpose, although other alloys of nickel and stainless steel can be used as well. Unlike conventional steel core strings, the cathodic member of the string of the invention is the core itself. Thus, when compared to conventional steel core strings, the surface area ratio of anode to cathode is higher in this invention, which results in a slower rate of corrosion with otherwise the same difference in galvanic potentials. Furthermore, conventional windings for steel cores are more cathodic than the steel core, which further accelerates the corrosion rate in conventional strings. In this invention, the use of a more cathodic titanium core widens the number of alloy possibilities that can be used without adversely affecting the corrosion rate of the resultant string. Hence this invention makes it possible to produce the first completely corrosion resistant, all-metallic wound, musical instrument string, which has all of the positive tonal attributes of conventional steel-core metallic strings. The enhanced corrosion resistance made possible by this invention greatly increases string shelf-life, which is a positive benefit for manufacturers, and distributors, who otherwise have gone to great extremes to develop special and costly packaging and coatings to protect conventional strings from the elements that cause corrosion. Equally important, the corrosion resistance afforded by this invention makes it possible for strings to have longer life during use, since the strings of this invention will resist the otherwise detrimental effects of moisture and ions from dissociated salts, organic acids, and other contaminates that originate from human hands during instrument use.
If the strings of this invention are intended to be used on instruments with magnetic pickups, it is preferable for the winding to be ferromagnetic since the titanium core is non-ferromagnetic. The most preferred winding for this purpose is nickel, or a ferromagnetic nickel containing alloy, since the resultant string will also exhibit the benefits of excellent corrosion resistance. If ferromagnetic characteristics are not required for end use, nickel or nickel alloys can still be used as windings, but titanium or slightly more anodic alloys such as phosphor bronze can also be used. If a slightly more anodic metal such as a phosphor bronze alloy is used, enhanced performance can be achieved by treating either the wound string or the winding wire with a chemical compound from the azole family, including triazole compounds such as benzotriazole and 5-methylbenzotriazole. It has been found that these surface treatments significantly reduce the corrosion rate of strings made with phosphor bronze wound on titanium, whereas they have little to no effect on strings made with phosphor bronze wound around a conventional steel core.
It has also been determined that the strings of the present invention exhibit reduced tension at pitch when compared to equivalent diameter steel core strings that have been made with similar winding alloys. Thus, the present invention makes it possible to produce a plural set of metallic strings for use on instruments that otherwise must employ nylon strings, such as classical guitars. The preferred winding for the bass strings in such a set is titanium, while the preferred core is titanium for both the wound and non-wound strings.
The strings of the present invention are unique compared to conventional metallic steel core strings in that the stiffness is significantly lower at equivalent core and winding diameters, as well as at equivalent tensions. This is a significant attribute which translates to faster and easier xe2x80x9cfingeringxe2x80x9d and xe2x80x9cchordingxe2x80x9d, both of which are huge advantages for the practicing musician. In addition, the lower pressure required for fretting should also translate to longer fret life, and a lower frequency of maintenance and fret re-surfacing.
By the very nature of this invention, ductile metal or polymeric surface coatings are not required for protecting the speaking length of the string from corrosion; although it is not the intent here to limit the use of such coatings if so desired for other attributes. Given that the core of the string of this invention is the more cathodic member of the galvanic couple, surface passivation with ductile coatings such as tin is not necessary. On the other hand, the absence of a ductile surface coating can make it more difficult to sustain a tightly wound structure during manufacturing, particularly if the chosen windings are high spring tempered alloys with low ductility.
In such cases, the performance of the present invention can be further enhanced by applying a sheathing material, such as a metallic sleeve or crimpable swage, a metallic brazing or coating, or a polymeric sleeve or coating, to a region outside the speaking length of the string for the purpose of maintaining winding tightness both during the manufacture step and during end use. Although the sheathing as described here could be used within the speaking length, it is most preferable to use these materials outside the speaking length so as to minimize effects on dampening and vibration attenuation. In a preferred method, the core of the string is looped around a conventional ball end which serves as the initial fastening point for the winding during a traditional spiral winding process. Either one or both ends, but preferably both, is sheathed with a polymer either before winding (over the core), after winding (over the wound core), or before and after winding. The polymer can be in the form of a heat shrinkable tube comprised of materials such as Teflon(trademark) or other tetrafluoroethylene fluorocarbon polymers, PVC, and Kyna(trademark) or other polyvinylidene fluorides; a heat shrinkable wound filament such as nylon; or a liquid based coating. The coating can be either water borne, solvent borne, neat, thermosetting or thermoplastic; and can be cured via photochemical or thermal initiation means.
Any one of these polymers could be employed for purposes of the present invention; either separately or in combination. However, the most preferred method employs a heat shrinkable, semi-rigid, high tensile strength, polymer tube such as Kynar, which is placed over both ends of the wound string outside of the speaking length, and is heat shrunk over the windings to tightly encapsulate the windings around the core, thus eliminating the potential for stress relaxation and winding recoil. It is important that the sheathing be used outside the speaking length of the string, so as to avoid affecting the tonal qualities during string vibration. It is also important that the sheathing exhibit high tensile strength and low elongation under load, so that it can sustain the torsional recoil stress of the windings, and can also sustain the tensile stress imparted by the tuning tension, particularly at the ball end where the potential exists for lateral winding slippage. The sheathing near the ball end can also serve to protect the wood on the bridge from wear, which otherwise occurs from the continued use of unprotected metal strings. The heat shrinking step can be accomplished in this process by either applying heat locally to the sheathed end(s), or by heating the entire string during or after winding, via any means including resistance or convection heating.
The preferred heat shrinkable tube has an inside diameter that is initially greater than the diameter of the wound string, and has a final outside diameter after heat shrinking which is small enough to enable the string to be strung through the holes of tuning posts on conventional instruments. The performance of this string can be further enhanced if before the heat shrinking and winding steps, an optional coating base is applied to the core opposite the ball end, or a nylon filament is wound around the same end. Such a base can provide either enhanced friction or bonding between the core and winding during the winding step, and thus can either serve to maintain winding tightness by itself, or can be used together with the preferred heat shrinkable polymer sheathing, which otherwise encases the entire wound structure, but outside the speaking length of the string.
Regardless of the choice of materials for the sheathing (i.e., metallic or polymeric), it is preferred that the sheathing be employed outside the speaking length of the string so as to not affect tonal characteristics during string vibration.